In motor vehicles, friction clutches serve for the mechanical disengagement of the transmission from the internal combustion engine when, for example, the transmission ratio of the manual transmission is adapted to the current operating state of the internal combustion engine. For operating such a friction clutch, use is made of release bearings which can be moved axially by means of an actuating device and can be brought into contact with the disks of a clutch diaphragm spring.
A release bearing of a friction clutch which is designed as a diaphragm spring clutch is known from DE 10 2009 049 466 A1. The release bearing comprises inter alia a bearing inner race, a bearing outer race and a plurality of spherical rolling bodies which are arranged annularly between bearing tracks of the two bearing races and are guided in a bearing cage. The bearing inner race can be connected to a release element in a rotation-resistant manner, whereas the bearing outer race is of a freely rotatable design and can be brought into contact with radially inner spring tongues of a diaphragm spring of a friction clutch. The two bearing races delimit a bearing inner space which contains the rolling bodies and is partially filled with a bearing grease, which space is closed off at least axially on one side by a seal which is rigidly fastened on the bearing outer race and which butts against an outer cylindrical sealing surface of the bearing inner race by a sealing edge of a sealing lip. For increasing the sealing effect, the sealing lip is provided with a return structure radially on the inside.
A disadvantage of this release bearing is, inter alia, that the return structure of the sealing lip represents a comparatively delicate structure which is in wear-prone friction contact with the outer cylindrical sealing surface of the bearing race so that its pumping action, by which discharged bearing grease is to be delivered back into the bearing interior, is possibly not sustainably ensured.